1. Field of the Invention
The present invention relates to a display device including: a plurality of pixel electrodes; a counter electrode provided so as to oppose the plurality of pixel electrodes to form a display capacitor between each of the plurality of pixel electrodes and the counter electrode; a plurality of storage capacitor electrodes provided so as to respectively oppose the plurality of pixel electrodes to form storage capacitors therebetween; and a storage capacitor line electrically connecting together the plurality of storage capacitor electrodes, and the present invention also relates to a method for testing the same.
2. Description of the Background Art
When manufacturing a liquid crystal panel, various tests are performed in various manufacturing steps.
Japanese Laid-Open Patent Publication No. 7-333275 discloses providing shorting lines to various signal lines such as scanning lines and source lines around the edge of a substrate of a liquid crystal panel for a display test, performing a display test by giving various signals to the shorting lines, and shaving (cutting) off the shorting lines after the test. It also discloses separately providing test terminals for controlling various signal lines such as scanning lines and source lines using a plurality of transistors in order to perform further display tests after cutting off the shorting lines.
In the liquid crystal panel manufacturing process, the test terminals are cut off after performing various electrical tests and display tests on the liquid crystal panel. Thereafter, a polarization plate is attached to the display surface of the liquid crystal panel. In a polarization plate test performed after attaching the polarization plate to the liquid crystal panel, the liquid crystal panel is tested as to the presence/absence of minute defects such as a scratch on the polarization plate or foreign matter or bubbles stuck between the polarization plate and the substrate, wherein it is necessary to control the liquid crystal panel in a white display or a black display so that the defects, etc., are more conspicuous.
Test methods in which the liquid crystal panel is lit in a solid-pattern display such as a white display or a black display are generally classified into solid-pattern lighting tests in which signals are input directly to signal input terminals of scanning lines and data lines of the liquid crystal panel without using the liquid crystal driver IC, and actual driving tests in which signals are input to signal input terminals of scanning lines and data lines using the liquid crystal driver IC. In these tests, a test probe is used for inputting signals to the signal input terminals.
Recent liquid crystal panels include a total of about 4000 scanning lines and data lines for an XGA (Extended Graphics Array; resolution: 1024×768 dots) class and a total of about 6000 scanning lines and data lines for a UXGA (Ultra Extended Graphics Array; resolution: 1600×1200 dots) class, with the same number of signal input terminals for the scanning lines and data lines, whereby the signal input terminals are arranged at a very small pitch, which is typically 50 to 70 μm. Therefore, it is necessary to use an expensive test probe that can be used with a large number of terminals and a small terminal pitch. Moreover, another requirement for such a test probe is that there should be no contact failure between the test probe and the signal input terminals when controlling the liquid crystal panel in a white display or a black display so that it is possible to test the liquid crystal panel as to the presence/absence of minute defects such as a scratch on the polarization plate or foreign matter or bubbles stuck between the polarization plate and the substrate, in a polarization plate test, for example. However, in view of the number of terminals and the terminal arrangement pitch as shown above, it is believed that the limit for the contact reliability in an actual manufacturing process will be about 5% in terms of the contact failure occurrence rate even when using a probe alignment device with a high-precision alignment mechanism in order to ensure a positional precision of the test probe. In worst cases, a contact failure occurs and the display will not be lit normally, thereby leaving defects undiscovered and passing the defective product to the following step, thus resulting in a loss of work time or a loss of material in that step. Therefore, in order to minimize the occurrence of the contact failure, it is necessary to perform a test probe alignment operation and a test probe cleaning operation.